On Monday, a mIRC exploit was revealed that allows someone to crash your client by sending you certain DCC requests. Versions 6.00 to 6.11 are vulnerable to this, and mIRC 6.12 has been released to fix the problem.

There are already people roving the networks armed with the crash code trying to crash people's active clients, and they have already visited Nightstar. If you are running mIRC 6.00 to 6.11, for your own safety we urge you to upgrade to 6.12.